Good news has been hard to come by for environmentalists, especially during an election year with potentially record-breaking gas prices. (Yes that was former President Bill Clinton at the ARPA-E summit on Wednesday telling greens they should “embrace” the controversial Keystone XL oil sands pipeline.) But there was good news to be had on Wednesday: two aging coal-fired plants in Chicago—blamed for respiratory illnesses in the city—will be closing down years earlier than expected in a deal that was brokered between energy companies, environmental groups and Chicago Mayor Rahm Emanuel.

Nor is Chicago the only city pushing to close coal plants. On the same day, the power generator GenOn Energy announced that it would be closing 7 coal plants in the mid-Atlantic region, retiring 3,140 MW of electricity generating capacity by 2015. Altogether 106 coal plants have been moved towards premature retirement since the beginning of 2010, the result of tougher federal air pollution regulations and a determined campaign by environmental groups like the Sierra Club to organize local opposition to plants. The shift away from coal—by far the biggest single cause of man-made global warming and a major source of traditional air pollutants—is a signature success for the environmental movement at a time when global action on climate change has been hard to come by. “City by city, town by town, communities are standing up and saying no to coal, and saying yes to clean energy,” wrote Mary Anne Hitt, the director of the Sierra Club’s Beyond Coal campaign, in the Huffington Post. “This milestone demonstrates that a shift is well underway across the country, and we will not power our future with the energy sources of the 19th century.”

Well, it’s definitely true that communities across the U.S. are saying no to coal—but less clear they’re saying yes to clean energy with the same volume. Still, the end of the Fisk and Crawford coal plants in Chicago have been a long time coming. I visited the city on a broiling hot day in July to profile the local opposition to the plants:

On a 99F July Sunday, there’s no cooler place to be in Chicago’s Pilsen neighborhood than the public pool in Dvorak Park, where you can catch a fleeting breeze in this working-class, heavily Latino community. Unfortunately, the air in Pilsen isn’t very cool–and it isn’t very clean. Chicago’s air on July 17 was so polluted that the government recommended that children and people with respiratory ailments–too common in a city that has nearly double the national asthma-hospitalization rate–limit their time outdoors. “People are getting sick in Chicago because of the air,” says Brian Urbaszewski, director of environmental-health programs at the Respiratory Health Association of Metropolitan Chicago. “And it’s people who are living in neighborhoods like Pilsen that are getting the worst of it.”

That’s due in part to the 450-ft. brick smokestack that looms over Dvorak Park–the one the kids call “the cloudmaker.” It belongs to the Fisk Generating Station, a 326-MW station just a couple of blocks from the park that’s one of the oldest coal-fired power plants in the country. Its corporate owner, Midwest Generation, says it has reduced pollution from the plant in recent years and that closing the facility would cost jobs, but Fisk is still viewed by environmentalists and activists in the city as a major health hazard.

Indeed, one report by the Clean Air Task Force estimated that toxic emissions from the Fisk plant were responsible for 15 premature deaths a year. And then there’s the issue of environmental justice—both of these plants were located near low-income, mostly Hispanic neighborhoods. Chicago gets the electricity, but they get the bad air:

More people live within a mile of Fisk than any other coal plant in the country. Schools and playgrounds sit within sight of the smokestack. “You can feel it in your lungs when you live here,” says Leila Mendez, a longtime Pilsen resident. “My hope is that it will just be closed.”

Mendez got her wish. Chicago Mayor Rahm Emanuel brokered an agreement with Midwest Generation—the company that owns both the Fisk and Crawford plants—to shut them down early, with Fisk closing by the end of the year and Crawford by the end of 2014. The Chicago Sun Times reported:

Midwest Generation blinked in response to Emanuel’s threat to put his political muscle behind a long-stalled “Clean Power Ordinance” that would have given the Crawford and Fisk power plants a longer timetable to either clean up or shut down.

The mayor has now accomplished that goal — and the corresponding health benefits to area residents forced to breathe polluted air — without a City Council ordinance that could have been challenged and possibly overturned in court.

“It’s a lot cleaner. We don’t have to go through City Council meetings with more protests outside. It was just good to sit down and come to a workable solution together,” said a top mayoral aide, who asked to remain anonymous.

It’s a bit ironic that Emanuel brokered the deal to shut the plants, since during his time as White House chief of staff he was often blamed by environmentalists for standing in the way of tougher climate legislation. But it’s amazing what sustained grassroots pressure—plus a few legal threats—will do even to political leaders who don’t much care for the environment. And that’s really where the anti-coal campaign has succeeded—not so much by appealing to the climate risk of coal power, but rather by focusing on the local pollution and health problems that can be traced back to older plants.

That was the main reason why New York Mayor Michael Bloomberg gave $50 million to the Sierra Club’s Beyond Coal campaign last year:Coal has long been the archenemy of environmentalists, largely because of its role in adding to climate change; the carbon-heavy fuel is responsible for about 20% of global greenhouse gas emissions. But as climate politics become increasingly polarized and the chance of any national action on greenhouse gases evaporates, environmentalists are going back to their old playbook, focusing on health issues instead — a case that’s far easier to make and far harder for non-greens to dismiss. Think soot and asthma, instead of carbon dioxide and warming. “This is a public health issue, just like our efforts to stop smoking or help with malaria,” says Bloomberg. “The pollutants and the toxins are a big problem.”

There’s something else responsible for the coal phaseout as well: natural gas. Thanks largely to new supplies from shale gas and fracking, natural gas—which produces far less traditional air pollution than coal—has become incredibly cheap. That’s encouraged utilities to retire their oldest and most polluting coal plants, knowing that they can sub in natural gas cheaply. It’s not that renewables like wind and solar haven’t played a part as a coal substitute, but without cheap gas utilities would almost certainly be fighting much harder against those early coal retirements.

And that’s where the anti-coal campaign could be running into trouble. Natural gas wouldn’t be anywhere near as cheap as it is without fracking—yet fracking has energized and enraged the environmental grassroots, who’ve pushed the national green groups to take a harder stance on natural gas. No organization knows that better than the Sierra Club. As TIME reported, the Club took over $25 million in donations from the CEO of a natural gas company in the past—money that was allocated for the Beyond Coal campaign, a fact that shows just how much the natural gas industry believed it could benefit from the coal phaseout. Sierra Club eventually turned down any additional money from the gas industry, and the Club, like other big environmental groups, has taken a much more critical position on fracking and natural gas. But cheap gas requires drilling and fracking—and without it, getting Beyond Coal may not prove so easy.